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Aug 15 to 17, 2017 1LCPM-12 Conference, Pasadena, CA
Advances in Planetary Seismology Using
Infrasound and Airglow Signatures on
Venus
1JPL/Caltech; 2Caltech, Pasadena, CA, USA; 3ISAE, Toulouse; France 4IPGP, Paris, France
Email: [email protected]
1Attila Komjathy, 1Siddharth Krishnamoorthy 1James Cutts, 1Michael Pauken,, 1Sharon Kedar, 1Suzanne Smrekar, 1Jeff
Hall, 1Alan Didion, 1Balthasar Kenda, 1Xing Meng, 1Olga Verkhoglyadova, 1Walton Williamson, 2Jennifer Jackson, 3David Mimoun, 3Raphael Garcia and 4Philippe Lognonné
Aug 15 to 17, 2017 2LCPM-12 Conference, Pasadena, CA
Introduction
• Motivation
• Balloon infrasound technique for Venus
• Earth-based experience
• Modeling background on Earth
• Planned Phase 1 to 3 experiments on Earth
• Airglow measurements on Venus
• Conclusions
• Acknowledgements
Aug 15 to 17, 2017 3LCPM-12 Conference, Pasadena, CA
Motivation
• The planetary evolution and structure of Venus remain uncertain more than half a century after the first visit by a robotic spacecraft.
• To understand how Venus evolved it is necessary to detect the signs of seismic activity.
• Due to the adverse surface conditions on Venus, with extremely high temperature and pressure, it is infeasible to place seismometers on the surface for an extended period of time.
• Due to dynamic coupling between the solid planet and the atmosphere, the waves generated by quakes propagate and can be detected in the atmosphere itself.
• Our goals are:
• Detect seismicity using infrasound measurements and characterize seismic wave propagation in order to determine crustal structure
• Conduct complementary investigation of airglow phenomenology, atmospheric gravity waves and ionospheric disturbances
Aug 15 to 17, 2017 4LCPM-12 Conference, Pasadena, CA
Three Techniques Defined at KISS Workshop at Caltech to Detect Seismicity on Venus
2)
Airglow
imaging
from
orbit
1)
Infrasound
observation
s at 55km
and -10
°C
2) Classical
seismic
measurements
with surface temp
of 465 °C
1) Infrasound measurements
2) Airglow imaging and 3) Seismometer on ground (currently
infeasible).
Aug 15 to 17, 2017 5LCPM-12 Conference, Pasadena, CA
Earth: Generation of Infrasound by Quakes
• Earthquakes and
volcanoes on Earth
can be detected using
infrasound techniques
in situ or from space
• Measuring and
modeling techniques
of infrasound signals
on Earth are well
understood
Aug 15 to 17, 2017 6LCPM-12 Conference, Pasadena, CA
Venus Epicentral and RayleighInfrasound Waves
60km
150km
Venus: Epicentral
Infrasound
Secondary Rayleigh
Infrasound• Seismic signals
couple 60X more
efficiently into the
atmosphere on Venus
than on Earth
• Infrasound wave
replicas of seismic
waves are near
perfect
• Almost no attenuation
below 80 km for
frequency < 1Hz,
hence use balloons
Aug 15 to 17, 2017 7LCPM-12 Conference, Pasadena, CA
Completed Aerostat Experiment: Altitude
Up to 1300 Feet on June 28, 2017
Infrasound signatures associated
with Rayleigh waves
Source: Seismic hammer
Objective:
Detect highly reproducible signal
Benefit: Validate 2-barometer
signal processing using point
source
Barometer 1
Barometer 2
(photos of actual experiment)
Aug 15 to 17, 2017 8LCPM-12 Conference, Pasadena, CA
Altitude
Phase 1
Balloon
Climbing
Phase 2
Tether / Baro
Deployment
Phase 3
MeasurementPhase 4
Tether / Baro
withdrawal
Time
T≃2-3 hours
Hmax< 1 km
Seismic hammer with the hot air
balloon monitoring ground strikes
Completed Piloted Hot Air Balloon Experiment:
Altitude Up to 3000 Feet on June 28, 2017
Seismicline
Trilliumx2 AcquisitionMicrophones
x2
Barometer
Needofsyncrhonization
ISAE
JPL
Aug 15 to 17, 2017 9LCPM-12 Conference, Pasadena, CA
Super
Pressure
Balloon
Flight
• Conduct tropospheric test flight collecting infrasonic data over
remote area
• Develop payload system
• Complete test data analysis
• Compare measured and modeled infrasound signatures
Phase 2 on Earth
Aug 15 to 17, 2017 10LCPM-12 Conference, Pasadena, CA
Prior Evidence of Ground Detection of Seismo-Acoustic Waves Generated by Earthquakes
Probing the Interior Structure of Venus 34
the bottom ones show pressure variations recorded at the same time; the two signals are
remarkably similar over a wide frequency range—the infrasonic signal is really a seismic signal.
The rapid growth in the number of Infrasound Monitoring Stations (IMS) over the last
decade complemented by expansion of regional networks such as those in Utah, has led to a
rapidly expanding knowledge of the acoustic signatures from not only earthquakes55
but also
volcanoes56
and meteors57
. In the case of earthquakes, this has recently resulted in more detailed
knowledge of the mechanisms by which seismoacoustic waves are generated. Studies of small
earthquakes such as the Circleville Utah, magnitude 4.7 event of January 3, 2011, which was
observed by all nine stations or the University of Utah’s infrasound array,58
have been
particularly useful. Two of the participants in the workshop (Arrowsmith and Blom) have been
actively involved.
This trace of a small earthquake (Figure 6-2) was detected at all nine stations of the array,
which extends across much of the state of Utah. The large signals in the spectral range 1 to 5 Hz
bounded by the red lines are ‘epicentral sound’ signatures that propagate entirely within the
atmosphere. The red lines denote group velocities of 0.34 and 0.22 km/sec). These epicentral
sound signatures were not seen at the three closest sites because there was no ducting of sound to
these locations. The other signatures that are prominent for the closer stations but occur for more
distant stations also correspond to ground-air coupled infrasound resulting from Rayleigh waves
(see Figure 4-10).
These investigations provide great insight on the mechanisms of generating seismic waves
for earthquakes of smaller amplitude. Although a much smaller fraction of the seismic energy is
coupled into the Earth’s atmosphere than would be the case on Venus, it is still sufficient for
detection of comparatively small events. Accordingly, the instrumental and analytical framework
is in place for applying seismoacoustic techniques on Venus.
Figure 6-2. Centerville earthquake 2011. Signals from the nine stations in the University of Utah array are shown. This is filtered data in the 1 to 5 Hz passband.
Epicentral
infrasound
Local
infrasound
Centerville Earthquake 2011 M 4.7 . Signals from the nine stations in
the University of Utah infrasonic array (1 to 5 Hz)
Epicentral infrasound from a M 4.7 earthquake was detected
at six infrasound stations extending up to 500 km from the
source
Sta
tion ID
Time (Min)0 453015
Reproduced from the paper by
Arrowsmith et al 2012)
Aug 15 to 17, 2017 11LCPM-12 Conference, Pasadena, CA
Proposed Oklahoma Test Site
Map of Oklahoma
The site chosen for this test is the north-eastern corner of the state of
Oklahoma where the frequency of earthquakes is the highest in the nation as
a result of pumping of waste water from oil drilling into geological formations.
Notional Stratollite
footprint
Aug 15 to 17, 2017 12LCPM-12 Conference, Pasadena, CA
Perspectives for Venus
Use of two barometers
(A) enables spatial filtering for separating
an upward traveling wave associated
with a quake from other sources of
pressure variability.
(B) In addition, infrasound waves
generated by Venus quakes are
faithful replica of seismic waves.
A
B
Aug 15 to 17, 2017 13LCPM-12 Conference, Pasadena, CA
Looking Ahead: Airglow Mission
Our mission concept VAMOS (Venus Airglow Measurement
and Orbiter for Seismicity) will measure atmospheric
perturbations from an orbiting platform that could provide a
breakthrough in detecting seismicity on Venus and in the
monitoring of seismic wave propagation.
Aug 15 to 17, 2017 15LCPM-12 Conference, Pasadena, CA
Conclusions
Balloon Experiments:
• We develop a novel technique and a balloon mission opportunity
for studying the seismicity and interior structure of Venus.
• The new technique will help discriminate for the first time between
quakes-induced signals and background with magnitudes ~3
and above on Venus.
Airglow Mission Concept:
• We expect to launch SmallSat (<180 kg) into high earth orbit as
rideshare with larger spacecraft
• Our mission concept VAMOS (Venus Airglow Measurement and
Orbiter for Seismicity) will measure atmospheric perturbations
from an orbiting platform that could provide a breakthrough in
detecting seismicity on Venus and in the monitoring of seismic
wave propagation.
Aug 15 to 17, 2017 16LCPM-12 Conference, Pasadena, CA
Acknowledgements
The research is funded by KISS and JPL R&TD program and carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.
Copyright 2017. All rights reserved. Government sponsorship acknowledged.
Aug 15 to 17, 2017 18LCPM-12 Conference, Pasadena, CA
Balloon Infrasound Objectives
• JPL in collaboration with ISAE and Caltech Campus is in a process of developing an instrument to measure seismic activity on Venus by detecting infrasonic waves in the atmosphere.
• The overall objective of this research is to demonstrate the feasibility of using sensitive barometers to detect infrasonic signals from seismic and explosive activity on Venus from a balloon platform. Because of Venus’ dense atmosphere, seismic signatures from even small quakes (magnitude ~3) are effectively coupled into the atmosphere. The seismic signals are known to couple about 60 times more efficiently into the atmosphere on Venus than on Earth.
• Our specific objective is to use two or more infrasonic sensors using barometers on a tether deployed from the balloon in a series of Earth-based tests.
Aug 15 to 17, 2017 19LCPM-12 Conference, Pasadena, CA
VWE Stated Stratollite Capabilities
Courtesy: https://worldview.space/fly-your-payload/
Aug 15 to 17, 2017 20LCPM-12 Conference, Pasadena, CA
Using Seismic Waves to Map Interior Structure of Venus
KISS VENUS-11
Nightside Airglow
imaging
Balloon(s) @ 55 km
Aug 15 to 17, 2017 21LCPM-12 Conference, Pasadena, CA
Wave-Propagation Global Ionosphere-Thermosphere Model (WP-GITM) Derived TEC Perturbations
Meng et al., 2015
Meng et al., 2017 (in
preparation)
[not to scale]For Tsunamis For Earthquakes
Input II
Tsunami wave
characteristics
Input I
solar wind
conditions, solar
irradiance, auroral
particle
precipitation
Input II
vertical velocity
data
Output
Ionospheric and
thermospheric
disturbances